Final answer:
During swallowing, or deglutition, there is a momentary cessation of breathing known as deglutition apnea, which allows for the safe passage of food into the esophagus without entering the respiratory tract. The exact percentage of swallows occurring during expiration is not detailed in the references, but the pharyngeal phase of swallowing ensures no aspiration into the lungs.
Step-by-step explanation:
The act of swallowing, or deglutition, is complex and involves several phases. The involuntary action that includes swallowing occurring during flight and effectively blocking the respiratory tract to prevent aspiration of food into the lungs is known as deglutition apnea. This process briefly halts breathing to permit safe passage of the bolus into the esophagus.
During the pharyngeal phase of swallowing, the epiglottis closes to block the airway, ensuring that swallowing occurs safely without food entering the respiratory tract. It is during this phase where breathing momentarily ceases, emphasizing the mechanism that protects the airway during deglutition. Although this question's figure or percentage is not specifically mentioned in the provided reference texts, it can be presumed that this cessation of respiration happens quickly and is an integral part of the swallowing process.